Try using Hitman Pro, Kaspersky's TDSS Killer you may also want to try Sophos Anti-Rootkit. All mentioned programs are free(hitman has a 30day trail). You mentioned that you are using AVG. Most of the times antivirus programs are unable to detect rootkit infections, try the mentioned programs above.
Just an FYI. I had the exact same problem with AVG identifying IRP hooks. So I ran Hitman Pro (free edition) and it identified a couple of rootkit issues/remnants. Hitman Pro removed them. I reran the AVG rootkit scan and it came up clean.
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